Deprenyl stimulates the efflux of monoamines from the rat hypothalamus in vitro

The direct effects of L-deprenyl, a monoamine oxidase inhibitor, on the hyp othalamus of male Sprague-Dawley rats was investigated by measuring the eff lux of norepinephrine (NE), dopamine (DA), serotonin (5-HT), dihydroxypheny lacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (B-HIAA) using a combi nation of high performance liquid chromatography with electrochemical detec tion and an in vitro incubation system. After measuring basal efflux by inc ubating the hypothalami with Krebs-Ringers Henseleit (KRH) alone during the first incubation period, hypothatami were incubated either with the medium , KRH alone (0 mM), or KRH containing 0.1, 1, and 10 mM L-deprenyl. During the third incubation period, hypothalami were again incubated with KRH aton e to measure the residual effects if any. During the final incubation perio d, the hypothalami were stimulated with high K+ KRH. Deprenyl produced a do se-dependent increase in the efflux of NE, DA, and 5-HT from the hypothalam i. Neurotransmitter efflux returned to pretreatment levels when L-deprenyl was removed from the medium. In contrast to NE, DA, and 5-HT, the efflux of the metabolites DOPAC and B-HIAA was inhibited in a dose-dependent fashion after incubation with L-deprenyl. Results from this study demonstrate that L-deprenyl is capable of stimulating the efflux of neurotransmitters in vi tro by a direct action on the hypothalamus. (C) 2001 Elsevier Science Inc.